A known parking assist apparatus is disclosed in JP2003-237511A (hereinafter referred to as Reference 1). According to the parking assist apparatus disclosed in Reference 1, while a vehicle is being guided to move rearward from a stop position to a target parking position, the vehicle is driven once away from the target parking position, i.e., the vehicle moves forward. Specifically, in a case where it is impossible to establish a driving path to the target parking position even with a maximum steering angle of the vehicle from the stop position, a driving path to a first target position located in the vicinity of the target parking position is established. Then, the vehicle is guided rearward along the driving path to stop at the first target position. Next, a driving path to a second target position to which the vehicle is guided to move forward is established. The vehicle is guided forward along the driving path to the second target position. In a state where the vehicle reaches the second target position, the vehicle is highly possibly guided to the target parking position directly from the second target position.
In addition, JP2008-284969A (hereinafter referred to as Reference 2) discloses a parking assist apparatus in which a vehicle is stopped at a position where a parking space can be confirmed (i.e., a tentative stop position) and where a parking assist is started by an operation of a switch.
According to the parking assist apparatus disclosed in Reference 2, division lines marked on a road surface, and the like are obtained by an image data captured by a camera to thereby detect a parking space, which is determined as a target parking position. Next, a driving path calculating portion calculates a tentative driving path based on a tentative rearward movement start position of the vehicle so as to determine whether or not the vehicle reaches the target parking position. Such calculation is repeatedly conducted while the vehicle is moving forward from the tentative stop position. In a case where the driving path to the target parking position is established, an alarm output portion informs a driver of the establishment of the driving path via a speaker, and the like. When the driver stops the vehicle upon recognizing the output from the speaker and starts an operation to drive the vehicle rearward (i.e., shifts a shift lever to a reverse position), a guide portion guides the vehicle to the target parking position by an automatic steering by which a power steering unit is controlled so as to move the vehicle along the driving path.
In a case where the vehicle is guided rearward to a predetermined target parking position, depending on a relationship between the target parking position and the vehicle, a relationship between the target parking position and an orientation of the vehicle, and the like, the vehicle may not be directly guided to the target parking position. That is, the vehicle may be required to be driven rearward and forward before being guided to the target parking position.
Reference 1 discloses the parking assist control in which the vehicle is guided forward once before being guided to the target parking position (which is defined to be a forward turning).
In a case where the driving path is specified beforehand from the stop position of the vehicle to the target parking position as described in Reference 1, for example, the vehicle may not avoid an obstacle that exists on the path of the vehicle moving forward and therefore may hit the obstacle.
In addition, in a state where a parking space is defined to be adjacent to a relatively narrow road, in the similar situation as that where an obstacle is present, the forward turning may be necessary to achieve parking the vehicle. A technique for guiding the vehicle to the target parking position including the forward turning is desired accordingly.
According to the parking assist apparatus disclosed in Reference 2, the driving path for guiding the vehicle to the target parking position is repeatedly calculated while the vehicle is moving forward. As a result, the volume of information processing is large, which may lead to a certain apparatus having a high processing capacity. In addition, when comparing the parking assist apparatus disclosed in Reference 2 with the parking assist apparatus disclosed in Reference 1 in which the vehicle is guided along the driving path determined in the parking assist control, the driving path along which the vehicle is driven is relatively flexibly specified according to the parking assist apparatus in Reference 2. However, because the forward turning is not assumed in Reference 2, a forward moving distance of the vehicle may be longer when an initial stop position of the vehicle (i.e., the tentative stop position) is inappropriate.
A need thus exists for a parking assist apparatus which is not susceptible to the drawback mentioned above.